The regulated standard set by the FDA (Food and Drug Administration) and WHO (World Health Organization) for pasteurizing an in-shell chicken egg is a 5 log reduction of Salmonella Enteritidis. Currently, the most commercially effective way to pasteurize shell eggs is to use an in-line water bath process to heat the shell eggs. The in-line process must sufficiently heat the entire egg, including the center of the yolk, for a sufficient amount of time to meet or exceed the 5 log reduction standard. For commercial reasons, it is important that the 5 log reduction is accomplished without overcooking the eggs. In some in-line commercial systems, a series of carriers are loaded with stacks of eggs and then sequentially submerged in and moved through the water bath according to predetermined pasteurization protocols selected for the size and start temperature of the eggs being pasteurized. Pressurized air is also supplied into the water bath to perturbate or agitate the water around and throughout the stacks of eggs, and to facilitate uniform heating of the eggs throughout the stacks. FIG. 1 shows a typical carrier 112.
Each batch of eggs brings with it the possibility of fluctuating thermal loads even if the eggs are tempered to a constant start temperature, such as 65° F. The system described in U.S. Pat. No. 9,289,002 entitled “Shell Egg Pasteurization Method” by Hector Gregorio Lara, issued on Mar. 2, 2016 therefore uses multiple individually controlled heating elements to accurately maintain the water bath temperature at the selected temperature set point. The heating system also includes several temperature sensors (e.g. RTDs) placed in the vicinity of the individual heating elements, as well as temperature sensors located higher in the water bath along its wall. PID (proportional-integral-derivative) controllers aggressively heat the water bath to the selected temperature set point, and a separate PID-controlled cooling system predicts the onset of unwanted temperature spikes and activates to prevent any unwanted temperature spikes. Water bath temperatures are actively monitored and recorded for each batch of pasteurized eggs. Data is reviewable remotely in real time, and reports are generated automatically for each batch to confirm that appropriate pasteurization times and temperatures have been applied.
FIG. 2 is similar to FIG. 2 in the above mentioned Lara '002 patent and shows the sequential in-line movement of the batches 118A-M of stacked shell eggs in carriers 112A-M through the pasteurization bath 116. Batches of stacked eggs are dropped in the front end of the water bath 116. The level of water in the water bath is designated by the dashed line 114. The submerged batches are moved through the zones in the water bath according to predetermined time intervals, and then removed. The batches are kept in each stage in each zone for about 4-5 minutes according to the selected pasteurization protocol, which as mentioned are customized for each egg size and start temperature so that the eggs in the stack achieve at least a 5 log reduction in Salmonella Enteritidis without overcooking. The heating requirements for the stacks being placed into the water bath 116 are significantly greater than the stacks that are about to be removed from the water bath. The individually controlled heating coils (128A-D) located near the floor of the water bath are critical to maintaining a uniform bath temperature. An air source 120 provides pressurized air through tubing to openings 117 in the water tank 116 underneath the heating coils 128A-D, in order to agitate the water throughout and around the stacks of eggs and help maintain uniform bath temperature. FIG. 3 is similar to FIG. 3 from the Lara '002 patent and is a sectional view taken along line 3-3 in FIG. 2. FIG. 3 illustrates the use of several heating coils spanning above the floor of the pasteurizer bath. In actual commercial systems, a larger number of independently controlled heating elements, e.g. 40, are used than is shown in FIG. 3. FIG. 3 also shows temperature sensors 130A-D which are located in the vicinity of each of the heating coils 128A-D.
It is important that the pasteurizer bath and the carriers be washed periodically, for example daily or every other day. Currently, commercial in-line shell egg pasteurizers are cleaned manually. Typically, the cleaning process begins after the last batch of pasteurized eggs is removed from the bath. Empty carriers 112 are removed from the pasteurization bath and are staged on the floor next to the pasteurization bath for manual cleaning. Floating debris is also removed. When the carriers and stacks of eggs are removed from the pasteurization bath, the water level falls because the eggs and carriers consume a significant volume of the pasteurization bath. It is therefore necessary to raise the water level to near the top of the pasteurization bath for cleaning. At that point, a first cleaning agent, such as a heavy duty liquid alkaline cleaner, is added to the filled water bath. Then, the air perturbation system is turned on and the water temperature is maintained at about 120° F. while the agitated water/alkaline cleaner solution cleans the bath walls, heating coils, temperature sensors and other submerged components for about 30 minutes. The solution is then drained completely while workers rinse the walls of the water bath. Once the tank is empty, the drain is closed and workers spray the internal surfaces in the water bath with a foaming chlorinated liquid detergent. The workers also spray the carriers outside of the tank with the foaming chlorinated liquid detergent, as well as tank covers. Then, the workers scrub the tank inside and out, the covers and the carriers using scrubbing pads. The chlorinated foam is then rinsed inside the pasteurizer using a power washer. The outside of the pasteurizer, tank covers and carriers are rinsed as well using regular hose water. The equipment is sprayed with a solution of 200 ppm quaternary ammonium. Finally, the water bath is filled with water and hydrogen peroxide solution is added to a concentration of at least 200 ppm. At that point, the water in the pasteurizer is ready to be heated for production. It is desirable that the alkaline cleaner be replaced with a nitric acid solution on a weekly basis. As the pasteurizer operates, hydrogen peroxide in the water bath is deactivated. Therefore, hydrogen peroxide is added throughout the workday to ensure that the hydrogen peroxide level remains between 200 ppm and 1000 ppm. It is most desirable that the concentration of hydrogen peroxide be within the range of 250 ppm to 350 ppm; however, the amount of hydrogen peroxide necessary to maintain these levels fluctuates greatly from batch to batch. Quite often, an excessive amount of hydrogen peroxide is added unnecessarily.
The cleaning procedures discussed above are not only time consuming, but also require significant amounts of water and cleaning agents. One object of the current invention is to reduce the amount of space, water and cleaning agents needed to adequately clean an in-line, shell egg water bath pasteurization system. Another object is to automate the cleaning process, reduce the amount of time that workers need to spend cleaning the system, and reduce their physical exposure to cleaning solutions.